Devil's Piper — Sarah Rayne

On inheriting his grandfather's tumbledown Irish cottage, adjoining the grounds of an old monastery, Isarel West discovers some old sheet music composed by his grandfather, a notorious and scandalous composer from the 1930's.

The music is the almost-forgotten Devil's Piper Suite, and when Isarel starts to play it he has little idea of the sinister force at its heart - a force that brought tragedy to a twelfth century family of Italian violin-makers...  A force that charmed a Tudor King three hundred years later, with shocking consequences...   And a force that, as recently as the twentieth century, wove a dark and dreadful thread through 1940's Berlin.  

Isarel, in company with Brother Ciaran, whose Order has guarded the music's secret for centuries, sets out to trace the dark legend to its source.